Production of propylene via dehydrogenation of propane conventionally involves a low pressure product splitter that produces a polymer grade propylene (98 wt %+) stream, and little to no propane. These low pressure product splitters require the use of a heat pump to operate, which are costly to run.
Alternatively, as described in U.S. Pat. No. 8,013,201, a high pressure product splitter may be used in the propane dehydrogenation process. In this process, the high pressure column is heated via a closed loop heat exchange cycle, where a heat pump heats and pressurizes a heat exchange medium. The heat exchange medium is pressurized and fed to a heat exchanger where the pressurized heat exchange medium comes into indirect contact with a portion of the product splitter bottoms product. Similar to the use of the low pressure product splitter, the high pressure product splitter requires an external heat source to operate.
Production of cumene is commonly performed by alkylation of benzene with propylene. Conventionally, cumene production also produces a propane gas stream that requires refrigeration and liquefaction to be stored or transported. Low pressure steam may also be made as a by-product of cumene production. The low pressure stream typically cannot be used by the cumene plant's steam system, and in such instances the heat is rejected to air or cooling water.